Etching machine



ug- 15, 1961 J. sTRAUss 2,995,850

ETCHING MACHINE ATTORN EY5 Aug. 15, 1961 J. sTRAUss ETCHING MACHINEOriginal Filed Feb. 6, 1957 FIG.4

F I 6.5 2,44XA

INVENTOR.

ATTORNEYS Patented Aug. l5, 1961 2,995,850 ETCHING MACHINE JosephStrauss, Hopewell, NJ., assignor to Trenton Times Cprporation, Trenton,NJ., a corporation of Delaware vide an etching machine which is simpleand inexpensive in construction, yet which is efHcient and reliableoperation.

A still further object of the present invention is to pro- 5 vide anetching machine wherein the etchant uid is dsonlegglcatginaglgagnl 5132:tributed uniformly against the face of a plate disposed-ev 730,209within the machine. j

s Claims, (C1, 41-9) Other objects and many of the attendant advantagesof the invention will become more apparent when con- The presentinvention relates to a new and novel etchsidered in connection with theaccompanying speciiica- Y ing machine, and more particularly lto anetching machine tion and drawings wherein: e utilized in connection withprinting plates or the like. FIG. l is a perspective View of the etchingmachine The present application is a division of U.S. patent withportions thereof being broken away to illustrate the application SerialNo. 638,509, led February 6, 1957. principle of operation; y The presentinvention is especially adapted for use in FIG. 2 is an enlargedsectional view illustrating theV etching magnesium plates as one step inthe processing plate rotating means embodied in the etching machine;thereof as, for example, described in the method disclosed FIG. 3 is a-sectional view taken along line 3-3 ofl in my aforementioned copendingapplication. Etching FIG. 2, looking in the direction of the arrows; jy., operations on printing plates are often a critical matter FIG. 4 isa front elevational view of the assemblyv since the `depth of the etchesis very important to achieve shown in FIG. 2; A' the desired results.Accordingly, etching operations ordi- FIG. 5 is a transverse sectionalview through the etchnarily required Ia very skilled operator in orderto achieve ing machine illustrating the cover construction and detheproper degree of etch. It is a primary concern of the tails of theexhaust ducting system; f present invention to provide an apparatuswhich may be FIG. 6 is a transverse sectional view taken through one 4quickly and easily adjusted, and is fully automatic in of the paddleassemblies; t operation whereby the skill required of an operator isFIG. 7 is an elevational view -showing an end portion. reduced to a ofone of the paddle assemblies; Y Numerous prior art devices have beenconstructed for FIG. 8 is an elevational view illustrating the mountingperforming etching operations, and one of the problems assembly of oneof the paddle shafts; and which has been encountered is the fact thatthe etching 30 FIG. 9 is a partial perspective view of an end portion I.fluid has a tendency to become concentrated in certain of one of thedeecting boards and illustrating adjustablev areas thereof greater thanother areas thereby causing an mounting means associated therewith. yuneven etch to be made. It is conventional practice in Referring nowmore particularly to the drawings' etching machines of this type toraise and lower paddleV wherein like reference characters designatecorrespond-V 'y assemblies within the machine to control thedistribution ing parts throughout the several views, the etching inaorspray of the etching fluid. This, of course, requires a chine is shownmost clearly in FIG. 1 and is constructed rather complex and bulkyarrangement which is awkward of generally rectangular form and isprovided .with v ai' to operate. vertical rear wall 278 and a front wall279 spaced therel The new and novel structure, according to the presentfrom with side walls 280 interconnecting the front andVl` invention,incorporates a pumping system which is em- 40 rear walls as well as abottom wall 281- so as toform', f ployed to distribute the etching fluidfrom a reservoir an enclosure Within which a plate 282 isdisposed'during'fsupply to a plurality of troughs from whence theetching the etching process. On the inside of the tank and alongu iluidis distributed to the printing plates by the paddle the bottom thereofis provided an open top trough `283. assemblies The pumping systemdistributes the etching and a similar trough 284 ,is disposed in spacedparaluid from the reservoir to the troughs, thereby effecting lelismthereto as is shown most clearly in FIG-' l. Each, f a continuousagitation and mixing of the etching iluid to of vthese troughs extendscompletely in between the sidev prevent concentrations of weak etchingiluid. Rather than walls of the machine and associated with each ofthe'sferl` providing adjustable paddle assemblies -as is common introughs is a paddle assembly, the ends of'twhich aref;` the prior art,the pumping system is so employed for con- Y shown in FIG. l anddesignated by the reference char-ll trolling the level of the etchingiluid within the troughs acters 285 and 286. Y 'j of the device so thatthe amount of etchant distributed Each paddle assembly incorporates aplurality fii by `the paddle assemblies is thereby controlled withoutsplashing blades which dip into a supply of etchingl ,solu-`necessitating any movement of the paddle assemblies. tion received inthe respective tanks 283 and 284 and, Easily accessible controls areprovided on the exterior of when rotated, splash or spray the etchingsolution for-5 l' the machine whereby an unskilled operator may make awardly to distribute it more or less evenly against the i few simpleadjustments and accurately control the etchface of the plate 282disposed Within the machin'el- The ing operation. The controls are soconnected that an tanks 283 -and 284 are connected directly to the ralYoperator may actuate the paddle assemblies either conwall 278 of vthemachine and the paddle assemblies-285 jointly or either paddle assemblymay be operated sepa- `and 286 are journalled in the side Walls 280, aswill .j rately. more fully described hereinafter. With the'particulr" Anobject of the present invention is to provide a new arrangement shown,there are actually three supplies of and novel etching machine which maybe quickly and etching uid within the interior of the machine."` Thefeasily operated and which minimizes the skill required iirst supply,which is actually a reservoir, is contained infn; of an operator. thebottom portion of the machine forwardly of the lowerj" Another object ofthe present invention is to provide trough assembly 283 `and the levelof such supply will, at" an etching machine which substantiallyeliminates connot time, except the height of the trough' 283 softhat y'centrations of weak etching fluid. there is no communicationtherebetween. The other'tv'vo l A further object of the presentinvention is to provide supplies are contained within the troughs 283and' 284 an etching machine wherein the distribution of etchant and apumping system is employed to distribute the etch-7^' may be easilycontrolled, and the paddle assemblies of ing uid from the rst mentionedreservoir supply 'i the machine may be individually operated.

the two troughs 283 and 284 and this forms an impc,l Yet another objectof the present invention is to propart of the etching machine assemblyinasmuch it ef Y 3 fects-ea `VcontinuousA agitation and mixing of theetching uid so that the tendency for concentrations of spent orweakeching fluid are not apt to occur.

Thepumping "system-embodies one or more pumps such as'ithoseiindicatedby the reference characters 287 and A 288, eachhaving a driving meanssuch as the electl'icftllot'ors1 289 and 290. lThe inlet of each pump isso co'nnctedas'to pickvup'the etching uid from the bottomofil'the-'main'freservoir or supply chamber within the etching`machine,as for example, by means of the inlet pipe" 291"`"sl'iown connected tothepump 288 and being 'p Iinto 'theletching machine through the opening292 in `tzlrebctto1i1 wall 281. The other lpump 287 is provided wthla,similar inlet pipe 293. The outlet of each pump is 'cqnnectedhrough avalve mechanism suitably accessibleto the operator and discharges' intoone or the other or both of Avthe troughs 283 and 284. For example, the288` is provided with the Voutlet line 294 which preferably ex'tendsup'along the side wall 280 to a valve 295" an'd"thence connects with ahorizontally disposed distribution line296 having'connections 297 and298 discharging :through theV back wall 278 and into the upperrnosttrough 284, whereas the other pump 287 is provided with a similardischarge or outlet line 299 leading to the valve 300 and thence to thedistribution line 301having the outlet connections 302 and 303discharging'into lthellower trough 283.

Inetching machines of the general character herein de` scribed; Iitisconventional practice to raise and lower theI paddle assemblies 285 andA286 so as to provide a greateror' lesser ldistribution or spray ofetching uid upon `the associated plate, the level of etching fluidremaining 1substantially constant within the reservoir supply 'beneathor associated with the paddle assembly. However-,z the present inventioncontemplates the use of Ipaddle assemblies which, during the normaloperation of the'machine, are fixed and wherein the pumping system'associated therewith in the specific embodiment shown inv FIG. Vl and asdescribed above is so controlled asto'ipermit the raising or lowering ofthe etchant uid within the troughs 283 and 284 so that the amount ofetchant :sprayed or distributed by the paddle assemblies is therebycontrolled without necessitating any movement of-fthe paddle assembliesthemselves.

Furthermore, in the specific embodiment shown, the individual paddlesand their troughs with their individual pumping systems permit theindividual control of the spr-ay'issuing from each paddle assembly. Thatis, by utilizing'a 'separate pumping system for each paddle asseibly,thelpaddle assemblies may be individually con-v trolrlled. This' isaccomplished by means of the valves 29'5an'd 300which can be manipulatedby the operator tohpreset the Yow characteristics in the distributionlines 296V and; v301 so as to maintain'any desired level of etchantwithin the troughs 283 and 284, thus individually controlling the spraycharacteristics delivered by the individual'paddle assemblies 285 and:286.

The paddle assemblies themselves are constructed preferably in themanner which is shown most clearly in 'V6 and 7 wherein each Awill beseen to include a pluralityv of individual and separate sections 304,305, 306,` etc'. Preferably, each of these sections incorporates acentrally disposed hubportion 307 which is hollow so asto receivetherethrough a driving axle 308 or 309 as' shown in FIG. 1,'and with aplurality of blade members 310, 311, 312 and 313 projecting radiallytherefrom and equidistantly spaced' circumferential relationship asY"sho'v'vn most clearly in FIG. 1. The con-tour of each ofthe/blades ispreferably similar to that shown in FIGQG wh'erein there is only aslight concave curvature offtheblades as presented to the etchant duringnormal rotation ofthe paddle assembly, the rotation -being clock-WiseinFIG. 6. It is'important to note, in connectionvWift'li,fthecontour?ofY the blades,-that there is no sharp trap theetchant Vas the paddle is rotated, and the curvature is substantiallyuniform and to such a small degree as to permit the etchant to be thrownfrom the paddle assemblies in its entirety wihout any amount of theetchant being retained. This assures a uniform distribution oftheetchant as accomplished by the paddle'assemblies. Y Y

Each of the sections 304, 305, etc. also includesta circularside' plate314 and when al-lof the sectionsy are mounted upon the associateddriving shaft, as is shown in FIG. 7, these side plates314,'=315,316,etc. abut adjacent blade assemblies, as shown, so as to forma unitarypaddle assembly and it 'is preferred, in this respect, that theindividual blades' be disposed in alignment withV each other along alength of the paddle `assembly as 'is shown in FIG. 7. j

The previously mentioned drive shafts 308 and309 ofthe paddle'assemblies`are journalled at opposite ends in the side walls 280v and at the otherend thereof project outwardly from the associated side wall and areprovided with means such as the pullies 317 and 318; For the purpose ofdriving each of the paddle assemblies, there may bemounted on suitablestands or brackets 319 and 320V driving means such as the electricmotors 321y andrv 322 operating through belts 323 and 324 to impart thenecessary rotation to the paddle assemblies 385 and 286. Referring atthis time more particularly to FIG. 8, the

manner of mounting the opposite ends of the paddle drive` shafts will beseen. On the outer side of theassociated side wall 280, there isprovided a generally L-shaped bracket member 325 presenting ahorizontally disposed outwardly projecting upper shelf portion 326having a pair of dipped holes receiving therethrough the elevating bolts327 and 328. The bolts 327 and 328 are connected to a pillow blockAassembly 329 and are rigidly affixed thereto, such pillow blockjournalling the associated end of the paddle drive shafts, such as thedrive shaft 308 as shown. Lock nuts 330 and 331 are associated with thebolts beneath the shelf 326 and when it is desired to make an adjustmentof the associated paddleassembly, these lock nuts are backed ol as wellas the lock nuts 332 and 333 associated withthe pillow block assemblyand the bolts 327 and 328 are turned to raise or lower thev pillow blockassembly and, consequently, the associated end of the shaft 308.` Whenthe proper adjustment is attained, the lock nuts are, lof course,re-tightened to hold the assembly rigid. The purpose of they pillowblock adjusting means is to permit the paddle `assemblies to be disposedin a direct horizontal position so that they will be uniformly disposedin partial submersions with relation to the etchant solution throughoutthe lengths of the `same so as to cause a uniformity in the spray actionimparted thereby across the entire width of the machine. This isnecessary, of course, inasmuch as it is 'easier 'to adjust thepositioning of the paddle assemblies than it is to level the entireetching machine with relation to the paddle assemblies whichwould'otherwise be necessary in order to achieve the properlrelationship between the etchant level and the paddle assemblies.

Cooperating with each of the paddle assemblies to provide 'the desiredspray characteristics is a baffle plate, indicated in FIG. 1 by thereference characters 334 and 3375, one of such bale plates being shownin partial de'- ftail more clearly in FIG. 9. YIn Vthe latter figure,the baille plate 334 will be seen to be provided at its ends withaxially projecting journals 336 which project through an arcuated slot337 in the associated side wall 280 and in lturn journalled within arectangular'plate member 338 'lying against the outer'sidc of theassociated side wall 280. A pair of wing nuts 339 and 340 projectthrough the plate 338 and cooperate therewith and with the arcuate slot337 to permit the journal end 336 to be located at will at any positionwithin the confines of the slot 337. n

thereof and suitable means, such as a set screw, not shown, or the like,may be utilized to fix the bathe plate 334 in any desired rotatedposition with relation to the plate 338. By this construction, theangularity of the baille plates as well `as the fore and aft positioningthereof may be adjusted at will to impart the desired characteristics tothe spray issuing from the associated paddle asj sembly.

FIG. illustrates Ithe construction of the upper portion of the etchingmachine and illustrates the cover structure therefore as well as aportion of the exhaust ducting therefor. In this figure, it will be seenthat the machine is provided with a partially enclosing top wall 341which projects forwardly from the back wall 278 and terminatessubstantially midway between the front and back walls as shown.Preferably, the inner end of the fixed top wall portion 341 is providedwith a rigidifying bead 342 of suitable configuration to impart sucientrigidity to this portion of the top to support the overlying slidablecover member 343. The cover member 343 when closed, extends from theinner face of the front Wall 279 to a point beyond the inner edge of thexed top wall portion 341 as shown and is provided thereat preferablywith a vertically projecting edge portion 344 serving as a convenientmeans to grasp the slidable cover and move it backwardly or to the rightin FIG. 5 so as to expose the top front portion of the machine to permitthe insertion of the magnesium plate and associated support assembly,hereinafter described, into the machine.

For the purpose of exhausting fumes from the interior of the etchingmachine, the same is provided with one or more exhaust fan structuresindicated generally lby the reference character 345 in FIG. 5, which aredisposed in vertical alignment below outlet portions 346 of an exhaustducting system. Associated with the fans 345 may be a shroud plate 347to direct the exhausted fumes toward the central portion of the fan, thefan being preferably of the centrifugal type.

FIG. l illustrates the manner in which the fans may be driven and, inthis respect, the rear wall 278 of the machine is provided with a pairof brackets 348 and 349 which support electric motors 350 and 351 havingdrive shafts projecting into the machine and mounting the eX- haust fanstructure. In this gure also, the exhaust ducting system 352 is moreclearly shown.

FIGS. 2 and 3 illustrate the construction of the plate supportingassembly and the manner in which the plate may be manipulated within themachine. In FIG. 2, reference character 353 illustrates a support plateformed of light-weight material, such as aluminum, and having aplurality of uniformly spaced perforations or holes therethrough whichare preferably closely spaced so as to render the plate as light aspossible. A magnesium printing plate or the like may be lfastened to thesupport plate by a number of suitable screw fasteners which projectthrough the holes provided in plate 353 to hold the printing platefirmly in place. Support plate 353 is provided with a hub 354 having abore 370 of substantially square cross-sectional conguration formedtherein. Square end 355 of support shaft 356 is disposed within bore 370and is journalled in a suitable bearing block 357 xed to the innersurface of the front Wall 279. A handle mechanism indicated generally byreference character 358 is fixed to the outer end of shaft 356. Hub 354is also provided with a notch 371 as seen in FIGS. 2 and 3, thedivergent side walls 372 and 373 of which flare outwardly from the bore370. `The notch, as seen most clearly in FIG. 2, is not as deep as thebore 370 so that when the support shaft 356 is engaged with the hub 354,the outer end portion of the square end 355 of the support shaft will berrnly sealed within the square socket portion defined by the bore 370beyond a notch of the hub. The purpose of the notch is to permit thesupport plate and hub to be easily engaged with the end of Support shaft356 since the divergent walls 372 and The handle assembly as shown inFIG. 4, is provided l with four radially projecting spokes 359, 360, 361and 362, the purpose of which Iwill be presently apparent. Fixed to theshaft 356 on the outer side of the front Wall 279 is a stop collarmember 363 serving to position the shaft 356 in its innermost position.The purpose of the handle assembly, constructed as shown, is to providean indexing means for the operator in performing the etching operation.That is to say, each etching operation is done on four sides of theprinting plate 282 and the spokes provide =a convenient index for theoperator to produce a quarter of a turn `on the support plate assembly353 and, consequently, the magnesium printing plate 282 attached theretoso as to alternately etch all four sides of the plate 282.

As previously described, the operator may control the spray volume bycontrolling the valves 295 and 300 and, consequently, the vamount ofetchant supplied to the troughs 283 and 284, raising or lowering thelevel therein to increase or diminish the spray volume, as desired. Theoperator also has access to a series of control switches along the upper`side of the machine and as are designated by the reference characters364, 365, 366, 367 and 368. These controls are, respectively, foroperating the llian, yfor rotating the lower paddle assembly, forrotating the upper paddle assembly, for operating both paddle assembliessimultaneously, and for energizing the two pumps. In addition to 'thesecontrols, there is a timer mechanism 369 mounted adjacent the controlsand preferably including a sweep second hand. By utilizing the controlsand operating them in accordance with a prescribed elapsed time, it ispossible to eliminate to a large extent, the skill required in theetching operating. In the event that it is desired to etch only certainportions of a plate, the plate should be placed in the machine and onlyone acid splash paddle assembly is utilized so as to direct the etchantonly against those areas of the plate which require etching.

It is apparent from the foregoing that there is provided a new and noveletching machine which minimizes the skill required of an operator toproduce proper and uniform results. The apparatus substantiallyeliminates any tendency for concentrations of weak etching Huid tooccur, and the necessity of moving the paddle assemblies to control theamount of etchant sprayed or distributed thereby is eliminated. Thepaddle Aassemblies of the device may be individually controlled and theyIadditionally provide a substantially uniform distribution of theetchant. The apparatus is simple and inexpensive in construction, andyet is eiiicient and reliable in operation.

As this invention may be embodied in several forms without departingfrom the spirit or essential characteristics thereof, the presentembodiment is therefore illustrative and not restrictive, and since thescope of the invention is defined by the appended claims, all changesthat fall Within the metes and bounds of the claims or that form theirfunctional as well as conjointly cooperative equivalents are thereforeintended to be embraced by those claims.

I claim:

l. An etching machine comprising a substantially rectangular tank `forcontaining a supply of etchant, a pair of troughs mounted within saidtank in vertically spaced relationship to each other for containingsupplies of etchant separate and distinct -from the supply contained bysaid tank, a pump system for circulating etchant from said tank to saidtroughs, a paddle assembly for each of said troughs and each projectingat least partially into its associated trough to contact the etchanttherein, means v for driving said paddle assemblies, means forcontrolling by said pump means to sepa- Y so constructed and arrangedthat etchant sprayed by each of said paddle assemblies is directedtoward saidmounting means such that the etchant will irnpinge upon anarticle supported by the mounting means.

2. An etching m-achine comprising a tank-like housing providing anetchant reservoir in the lower portion thereof, means for supporting aprinting plate in vertical position within said housing, a pair ofhorizontally disposed, vertically spaced open top troughs fixed withinsaid housing, the lower of -which is disposed such that its top is abovethe level of etchant in said housing, a paddle assembly associated witheach of said troughs, each paddle assembly includinga plurality ofclosely spaced -blades rotatably supported about a horizontal axis abovean associated trough so that theblades pass through the conlines of thetank during a portion of their rotary paths,

' meansV for rotating said paddle assemblies, means for circulatingetchant lfrom the housing reservoir to said troughs whereby-to maintainthe entire body of etchant in a state of iiow, means for controlling thelast mentioned means such that a separately variable predeterminedetchant level is selectively maintained in each individual trough whichis at least as high as the lowermost portion of the paddle assemblieswhereby the volume'of etchant thrown from the troughs is variable, saidpaddle assemblies and said support means being so constructed andarranged that etchant sprayed by each of said paddle assemblies isdirected toward said support means such that the etchant will impingeupon an article supported by the support means.

3. The assembly as defined in and =by claim 2 wherein the printing platesupporting means is manually rotatable to selectively position the platewithin the machine.

4. The assembly as detined in and by claim 2 including a deliector platemounted `within said housing above each of said paddle assemblies, eachdeflector plate being mounted for varying in angle to the horizontal andfor moving the same forwardly and rearwardly in said housing so as toselectively position its leading edge disposed closest to the printingplate.

5. An etching machine comprising a substantially rec:-y tangular tankfor containing a supply of etchant, a pairl ofV troughs mounted `'withinsaid tank in vertically spaced relationship to each other for containingsupplies of etch-v ant separate and'distinct from the supply containedby said tank, a pump system for circulating etchant from said tank tosaid troughs, a paddle assembly for each of said troughs and eachprojecting at least partially into itsassociated trough to contact theetchant therein, means for driving said paddle assemblies, means forcontrolling the ow of etchant eifected by said pumpV means to sepa#rately` control the etchant level within each individual trough andAthus determine the quantity of etchant splashed therefrom bysaid paddleassemblies, a defiector plate supportedwithin said tank above saidpaddle assembly for controlling the spray characteristics of the etchantprojected from the trough by said paddle assembly, and means forvmounting a printing plate within said tank for action thereon by 'theetchant splashedby said paddle assemblies,V said paddle assemblies' andsaid mounting means being so constructed land arranged that etchantsprayed by each of said paddle assemblies is directed toward saidmountinggmeans such that the etchant will impingeL upon an articlesupported by the mounting means;

6. An etching machine comprising a substantially rectangular tank forcontaining la supply of etchant, a pair of troughsmounted within saidtank in vertically spaced re.

lationship to each other for containing supplies of etchant separate anddistinct from'the supply contained by said tank, a pump system 'forcirculating etchantV from said `tank to' said troughs, a paddleassembly'for each of said troughs and each projecting at least partiallyinto its associated trough to contact the etchant therein, means fordriving said paddle assemblies, means for controlling the flow ofetchant effected by said pump means to sepa# rately control the etchantlevel within each individual' trough and thus determine the quantity ofetchant" splashed therefrom by said paddle assemblies, a deiiectorVplate supported within said tank above said paddle assembly forcontrolling the spray characteristics of the etchant projected from thetrough by said paddle assembly, adjustable mounting means for saiddeector plate" whereby the angularity of the deiiector plate withrespect to the horizontal maybe varied and including means for movingthe leadingedge of the deliector plate toward and away from a print-ingplate disposed within the tank, 'and means for mounting a printing platewithin said tank for' yaction thereon by the etchant splashed by saidpaddle assemblies, said paddle assemblies and said mounting means beingso constructed and arranged that etchantV sprayed by each' of 'saidlpaddle assemblies is directedY toward said mounting means such that theetchant will impingev upon an article supported by the mountingV forsupporting a printing plate in Avertical position within said housing,said supporting means being rotatable to selectively position the platewithin fthe machine, a pair of troughs mounted within said tank invertically spaced relationship to each other for containing supplies ofetchant separate and distinct from the supply contained in saidreservoir, a paddle assembly for each of said troughs and eachprojecting at least partial-ly into its associated trough tocontact theetchant therein, means for driving said paddle assemblies, pump meansfor circulating etchant from the supply within said reservoir to eachtrough so as to vcontinuously replenish the supply of etchant in eachtrough and maintain the entire body of etchant in agitated, circulatingflow, said pump means including a driven pump having its inlet connectedto said tank supply and having a first outlet conduit connected with oneof said troughs and a second outlet conduit connected with the other ofsaid'troughs, a separate controllable valve connected in each of saidconduits for selectively individually controlling the level of etchantin the diierent troughs to thereby eifectively vary the amount ofetchant distributed-by` the paddle assembly of veach `in"- dividualtrough, said paddle assemblies and said support means being soconstructed and `arranged that etchant 2.sprayed by each of said paddleassemblies is directedr Vtoward said support means such that theVetchant will impinge upon an article supported by the support means.

8. Apparatus as defined in claim 7, including a deector plate supportedwithin said tank above eachof said paddle assemblies for controlling thespray characteristics of the etchant projected from the trough bytheasso*- ciated paddle assembly,.each of said deector plates beingseparately and individually adjustable whereby the angu- Ilarity of eachdeflector plate may be separately varied.

References Cited inthe file of this patent` UNITED STATES PATENTS'1,267,754 Flick May .28, 1918 1,747,168 Holmstrom Feb. 18, 19301,825,127 Powers Sept. '29,V 1931 2,669,048 Easley et al Feb. 16, 19542,822,635 Mears Feb.`11, 1958 2,827,723 Clarkl Mar. 25, 1958

